This invention relates generally to transferring fluid from a vial with a sample probe without fluid carryover or contamination. More particularly, the invention is directed to a sample probe cleaning device which can be utilized to clean and dry the probe as desired.
Automated blood and blood cell analyzers are well known. These analyzers typically utilize a portion of a whole or pre-prepared blood sample. When the blood sample is taken from a subject, it usually is placed into a vial or test tube.
In some analyzers, a portion or aliquot of the blood sample then is aspirated from the vial by a sample probe. The probe can be moved into a fixed position vial or the vial can be moved to a freed position sample probe. The aspirated aliquot then can be dispensed from the sample probe or aspirated through the sample probe into the analyzer or into a sample preparation bath or a combination of various aspiration and dispensing steps.
In the most simple operation, the sample probe must be thoroughly cleaned and dried between aspirations of different sample aliquots to avoid carryover contamination. If the sample probe dispenses the sample aliquot, then the exterior of the sample probe must be washed and dried to avoid carryover which can adversely affect the volume of the dispensed sample aliquot. In cases of small volumes of sample aliquots, the excess sample carried on the exterior of the sample probe can be a significant volume with respect to or can exceed the volume of the dispensed sample aliquot. The carryover on the sample probe exterior thus can be a significant problem with the operation of a single sample aliquot and between different sample aliquots.
The prior art has provided various solutions to the carryover and contamination problem. Some analyzers include a manual sample probe wiping operation between each sample aliquot aspiration. This solution is not always effective and requires potentially intimate operator contact with the sample fluid and is not readily performable during a multiple-step operation in an analyzer.
In an attempt to solve these problems and to effectively automate the probe cleaning operation, the prior art has developed several types of probe wash chambers having a passageway into which the sample probe is inserted to clean the exterior and in some instances the interior of the sample probe. In general, the probe wash chamber includes a wash fluid input into the passageway and a fluid output or exhaust for removing the fluid once the exterior of the sample probe has been cleaned. The prior art probe wash chambers can leak fluid and also can channel along only one side or a portion of the sample probe which can leave residue on the probe exterior. This can contaminate the operation and also cause carryover problems. In an attempt to avoid the channeling problem, the Assignee of the present invention developed a probe wash chamber which included internal threading in at least a portion of the probe wash chamber passageway. The fluid input to the threaded passageway was at a tangent to the threaded passageway. This threaded passageway improved the sample probe washing operation, but still can allow channeling since the fluid input is not always into a threaded channel or groove and can just as easily be partially or wholly opening into the ridge between the threaded channels.
It therefore would be desirable to provide a method and apparatus for aspirating a precise sample aliquot with a sample probe without contamination and carryover on the sample probe exterior. It further is desired to wash the sample probe exterior while containing the wash fluid within a wash chamber.